Semiconductor wafers form the basis for the manufacture of integrated circuits onto semiconductor chips. Wafers undergo one or more types of processing resulting in the formation of microcircuits thereon. After processing, the wafers are cut into chips, with each chip containing an individual microcircuit.
The semiconductor wafers are of circular circumference and are very thin. The wafers, which are typically made of silicon or germanium, are fragile and as such are particularly vulnerable to breaking when handled. The wafers are typically stored in plastic containers or wafer boats. The wafer boats have a plurality of parallel transverse grooves or slots for receiving individual wafers.
One of the steps in the manufacture of some types of integrated circuits on the wafers involves placing the wafers in a high temperature oven wherein the wafers undergo a chemical diffusion process. Before the wafers are placed in the oven however, the wafers are transferred from a plastic boat to a wafer boat made of quartz. Quartz wafer boats are better suited to the high oven temperatures than are plastic wafer boats. When the diffusion process is complete, the wafers are then transferred back to the plastic wafer boat from the quartz wafer boat.
Prior art automatic transfer apparatuses transfer wafers from plastic wafer boats to open bottom quartz wafer boats. Both the plastic wafer boats and the open bottom quartz wafer boats are similar in that both have open bottoms which allow wafer elevators to enter the boats through the open bottom and push the wafers out through the top for removal. However, some types of quartz wafer boats are closed bottom and are therefore unable to receive wafer elevators from underneath the quartz boats. The only access into these closed bottom quartz boats is through the top. In the prior art, the wafers are transferred to and from closed bottom quartz boats manually. Such manual transfer is time consuming because of the large amount of time that must be taken to carefully handle each wafer, and costly because some wafers are inevitably broken in the transfer process. Therefore, what is needed is an automatic method of transferring wafers in and out of closed bottom quartz boats.
It is an object of the present invention to provide an apparatus that will automatically transfer semiconductor wafers to and from closed bottom quartz boats.